In the past various methods have been used to provide materials that are capable of filling the annular space between production tubulars and a wellbore wall in both cased-hole and open-hole wellbores. Such materials have been found to be useful for sand control and for isolating a portion of the formation. Sand control methods typically utilize gravel packing outside of downhole screens. The gravel inhibits or prevents the production of undesirable solids (such as sand) from the formation, while still allowing the flow of desirable production fluids. More recently, with the advent of tubular expansion technology, a downhole screen can be expanded in place to eliminate the surrounding annular space that had heretofore been packed with gravel. Such a method may not be practical in some cases due to wellbore shape irregularities. While a fixed swage can be used to expand a screen by a fixed amount, it does not always effectively address the problem of wellbore irregularities. Furthermore, a washout in the wellbore can sometimes result in formation of a large annular space outside of the screen, while an unanticipated area of small diameter in the wellbore can result in sticking of the fixed swage, causing problems in placing the fixed swage to the desired location. Flexible swages offer the ability to flex inwardly in tight areas, which may reduce the chance of sticking, but still have a finite expansion capability. Therefore, the problem of annular gaps or voids beyond the range of the swage remains substantially unadressed by these approaches.
Alternative screen designs have included use of a pre-compressed mat held by a metal sheath, which is then subjected to chemical attack when placed in a desired downhole location. Once in position the mat is allowed to expand from its pre-compressed state, but the screen itself does not expand. Some of these designs suffer from the problem of relatively rapid “locking in” of the space-filling means at a given location following its introduction downhole. This rapid “lock-in” in many instances can prevent or discourage the repositioning of the device for optimal performance and can result in costly remediation work.
Thus, there is a need for improved apparatus and compositions and methods for deploying the same in wellbores to perform various functions, such as filling annular spaces, isolating zones, proving seals, etc.